1. Field of Invention
This invention relates to apparatus especially designed for processing semiconductor wafers or similar disc-shaped objects. More specifically, the invention is concerned with providing an improved apparatus which permits easier or automated loading and unloading of carriers into and out of such apparatus for increasing productivity and quality of the processing carried on within the apparatus.
2. Description of Prior Art
It is known in the art of processing semiconductor wafers to provide for various forms of apparatus which allow the wafers to be coated, etched, cleaned, or dried, prior to eventual use of the wafers in the production of integrated circuits. Early efforts for treating wafers in these various ways involved the treatment of only a single wafer at a time, as shown for example in U.S. Pat. No. 4,027,686 or the treatment of a number of wafers in a stationary tub as shown, for example, in U.S. Pat. No. 4,092,176. Other developments included arrangements for spinning a plurality of wafers within a controlled environment so that multiple processing steps (such as washing with deionized water and drying with nitrogen gas) could be carried out during a single cycle of operations in a single apparatus. Representative patents showing this approach include U.S. Pat. Nos. 3,970,471; 4,132,567; and 4,300,581.
At the present time there appears to be a preference for processing a plurality of wafers in standard-sized plastic carriers which are used for holding and protecting wafers while they are being transported and processed. U.S. Pat. No. 4,300,581 discloses a type of apparatus designed to receive such standard carriers through an end opening of a rotor mounted within a stationary tub. The arrangement shown in U.S. Pat. No. 4,300,581 provides for a tilted axis of rotation which is described as solving a problem of liquid being retained between wafers because of surface tension. However, it is also stated in the same patent that horizontal loading of apparatus of this type is more desirable than loading on a vertical axis.